CVE-2025-26465Openssh: machine-in-the-middle attack if verifyhostkeydns is enabled

Description

A vulnerability was found in OpenSSH when the VerifyHostKeyDNS option is enabled. A machine-in-the-middle attack can be performed by a malicious machine impersonating a legit server. This issue occurs due to how OpenSSH mishandles error codes in specific conditions when verifying the host key. For an attack to be considered successful, the attacker needs to manage to exhaust the client's memory resource first, turning the attack complexity high.

Timeline

Scores

EPSS (exploitation in 30 days)

7.7% · top 5.3% of all CVEs (14 Nov 2026)

CISA SSVC

Exploitation: poc · Automatable: no · Technical impact: total

The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 6.8.

Affected products

• OpenSSH

  • affected 6.8p1 – ≤ 9.9p1

• Red Hat · Red Hat Enterprise Linux 8

  • unaffected 0:8.0p1-26.el8_10 – < *

• Red Hat · Red Hat Enterprise Linux 8

  • unaffected 0:8.0p1-26.el8_10 – < *

• Red Hat · Red Hat Enterprise Linux 9

  • unaffected 0:8.7p1-45.el9 – < *

• Red Hat · Red Hat Enterprise Linux 9

  • unaffected 0:8.7p1-45.el9 – < *

• Red Hat · Red Hat Enterprise Linux 9.4 Extended Update Support

  • unaffected 0:8.7p1-38.el9_4.5 – < *

• Red Hat · Red Hat Discovery 1.14

  • unaffected 1.14.3-1748529279 – < *

• Red Hat · Red Hat Enterprise Linux 10

  All versions: unaffected

• Red Hat · Red Hat Enterprise Linux 6

  All versions: unknown

• Red Hat · Red Hat Enterprise Linux 7

  All versions: unknown

• Red Hat · Red Hat OpenShift Container Platform 4

  All versions: affected

What to do

Workaround: This issue can be mitigated by disabling VerifyHostKeyDNS by setting that option to 'no' in an SSH client configuration file (such as /etc/ssh/ssh_config, ~/.ssh/config, or one of the files in the /etc/ssh/ssh_config.d/ directory). This is the default configuration in Red Hat Enterprise Linux. For configurations that require VerifyHostKeyDNS to be enabled (set to either 'yes' or 'ask'), mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• EUVD EUVD-2025-4686 (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2025-26465](https://cveledger.app/badge/CVE-2025-26465.svg)](https://cveledger.app/cve/CVE-2025-26465)

Record last updated 5 Nov 2026, 15:26 UTC.